1. Field of the Invention
The present invention relates to a wobble pump on which the invention is based operates on the following principle. When a drive shaft is turning a swash plate shaft is moved so as to describe a double cone about the center axis of the drive shaft. Owing to the oblique setting of the swash plate pump shaft in relation to center axis of the shaft a swash plate which is perpendicular to the swash plate shaft in a pump chamber accommodating it will perform a wobbling movement about a wobble point on the center axis of the drive shaft. A partition extending in the axial direction of the drive shaft and intersecting the swash plate divides the pump chamber into an intake part and a delivery part. Owing to the moving swash plate two circularly extending, variable-volume pumping spaces are produced within the pump chamber.
2. Discussion of the Related Art
A swash plate pump in which the swash plate is arranged in the pump chamber, whose housing surfaces opposite to the swash plate are spherical in form is disclosed in DE-B 1,090,966. The plane of the pump chamber extends perpendicularly to the plane of the drive shaft. Owing to the swash plate, which is arranged obliquely in the pump chamber, the pumping chambers are formed on either side of the swash plate which are variable in volume. The swash plate which is moving in the pump chamber is designed in the form of a circular ring, which is so arranged that its internal diameter lies on a spherical surface of a hub of the swash plate. This spherical surface is supported by a bearing in correspondingly formed mating surfaces of the pump housing which encloses the pump chamber. Since between such bearing surfaces medium is able to emerge from the pump chamber and to flow into the space comprising the swash plate shaft and then escape to the outsider an elastic boot seal is provided between the hub of the swash plate and the swash plate shaft bearing. At the one end such boot is connected with the stationary pump housing and at the other end of this boot is attached to a sleeve drawn onto the swash plate shaft and it is statically sealed at either end.
Although in the case of known swash plate pumps there is a hermetic termination of the space acted upon by the medium to be pumped so that the space is sealed off from the surroundings, this design means that there is a space with a low degree of liquid exchange between the pump chamber and the space comprising the swash plate shaft. This space consequently acts as a dead space, in which the medium collects and in which it remains substantially without any change. This design of pump is unsuitable for products which are likely to be damaged, as for instance foodstuffs or the like materials which have to be handled under highly hygienic conditions. The dead space means that each time the pump is stopped its housing has to be opened and thoroughly cleaned. Otherwise the medium present in the dead space would decompose, microbes or the like would find their way into the housing and would have a deleterious effect on the pumped medium.